Electrode clamp



y 30, 1933- w. N. MISCHLER 1,912,006

ELECTRODE CLAMP Filed May 29, 1929 'Fi l.

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1t J /z ,2 v /J /J g H i I 1 l a I! H .7 {L K- Inventor:

William Tlmischler Wm y 7 His Attorney.-

Patented May 30, 1933 UNITED STATES. PATENT FFNE VIILLIAM N. MISCY-ILER, OF SCOTIA, NEW/V YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION OF HEW YORK ELECTRODE CLAIviP Application filed May 29,

The present invention relates to electric discharge apparatus and more particularly to the supports for securing the electrodes within the glass envelope.

Electric discharge devices are usually constituted of an evacuated envelope containing a plurality of cooperating electrodes from which leads are taken to the exterior, the electrodes sometimes being immersed in a gas or vapor. The electrodes are most conveniently supported within the envelope from one or more reentrant stems, and are provided with collars which embrace each stem, the collars being secured to the stems by means of screw clamps. These collars are ordinarily made of Monel metal which offers advantages by way of being readily denuded of occluded gas and also as offering ease of manufacture, the metal being characterized by resisting rust or oxidation. The collars are fabricated out of thin stock and slotted in various ways in order loosely to fit about the encompassed stem before the clamp is applied but readily to allow a constriction of size when the clamping device is tightened suflicient to hold the collar and attached electrode in place. The clamping devices or rings have heretofore been made of the same metal as the collar, i. e. monel, in order to obtain the same advantages as are present with respect to the collars. It has been found in practice however, that notwithstanding the extreme tightness with which the clamp was applied about the collar there was present considerable slippage between the collar and stem under operating conditions. It was believed that the condition was a result of the low coefficient of friction between the smooth glass and metal surfaces and in order to improve the construction it has heretofore been proposed to insert copper gauze between these surfaces or even to sand blast or otherwise roughen the glass. Notwithstanding these expedients, there still remained sufficient movement between the contacting parts as to destroy the proper spacingbetween the supported electrodes and hence seriously to affect the operating characteristics of the tube.

An object of the invention is to provide 1929. Serial No. 366,996.

an improved clamping arrangement for rigidly securing the electrode support collar to a glass stem or to another body ofextrenie hardness. Another object is to provide an arrangement of this character as will avoid the necessity of employing frictional surfaces or devices between the conducting parts. Theseobjects are attained in brief,

by fabricating the clamping ring out of a v material, whose coefficient of expansion is less than the metal of the support collar. It will then be understood that as the temperature of the discharge device is raised during operation, the linear expansion of the metal clamping band is less than that of the collar and the glass stem, with the result that the band not only maintainsits grip on the collar and stem but may slightly increase the same thereby rigidly to secure the collar to the stem.

The invention will be more completely understood when reference is made to the following description and the accompanying drawing in which Fig. 1 illustrates a tube, partly broken away, with the electrodes, supporting collars and the improved clamping rings in place; Fig. 2 is an enlarged perspective view of the clamping ring.

Referring to Fig. 1, numeral 1 designates an evacuated envelope which may or may not contain gas, the envelope terminating at the ends in reentrant stems 2, 8, between which an electrode assembly is supported by means of collars 4, 5. This assembly may consist of a hollow anode 6 of the usual con struction suspended from the upper collar 4 by rods 7', 7 which are fastened to the electrode in any suitable manner; the collar 4 may be closed at the bottom to provide ma terial in which the rodsmay be anchored. The collar 4 also carries a plurality of lavite members 8 through which are threaded uprights 9 for mounting the grid and filament electrodes (not shown) within the plate member. The lavite member 8 nearest the stem is secured to the collar in any suitable manner, while the other two members 8, 8 are fastened to the uprights 9. There is a spacer 10 between these two members.

The grid is rigidly supported at the bottom by a metal flange 11 secured to the collar 5, while the several strands of filament enclosed within the grid and anode members terminate in tie wires 12, 12 to space the members apart and also leading-in conductors 13, 13 which are fused in the stem 3. It will be observed that the plate 6 is supported solely from the stem 2 by the collar 4t and that the grid is suspended between the stems by both collars 4. and 5, although its rigidity of position is provided for by the collar 5 since the uprights are not rigidly fixed in the uppermost lavite member 8 but a sliclable fit is ofiered by this member inorder to accommodate expansion of the grid and uprights during operation. Inasmuch as the plate and grid members of the larger power tubes are quite heavy, it is necessary positively to secure the collars a and 5 about their respective stems so as to hold these electrodes securely in place. These collars are ordinarily made of Monel metal (62% copper, 81% nickel, 3% iron, 2% manganese and 2% impurities) which has a higher coefficient of expansion than glass and hence under heated conditions the collar will expand and cause a loose fit on the stem thus necessitating some form of clamp. The collars normally contain longitudinal and transverse slots 14 to enable the collar readily to slide over the stem during assembly and to allow considerable contraction in size when clamped by one or. more metallic rings 15 shown in detail in Fig. 2. Heretofore it has been the practice to fabricate these rings out of Monel metal, i. e. similar to the metal of the collar,-but in accordance with my invention I propose to manufacture these members out of metal called invar, having a composition roughly of 36% nickel and 64% iron. The ring terminates in parallelly extending projections 16 which are rigidly secured thereto by flanges or ears 17. Through the projections there is threaded a screw-bolt 18 for drawing the two ends of the ring together thus serving to tighten this member about the collars 4, 5. As shown in Fig. 1, the envelope may also contain a capsule 19 attached to one of the electrode leads or other metal within the tube, the capsule enclosing getter material for absorbing deleterious gases within the envelope. It will be evident that inasmuch as the collaris made of Monel metal which has the coeflicient of expansion of .000049 per degree centigrade between 0 and 500 0., whereas the clamp ring is constituted of invar having a coefiicient of expansion of .0000023 per degree centigracle from 0 C. to 142 C, and .000003 from 150 C. to 250 0. hence of practically negligible expansion, the ring will increase its clamping effect about the collar under heated operating conditions because its rate of expansion is less than that of the collar metal; The collars 4, 5 thus grip the stems 2, 3 with an increasing compressional eifort as the operating temperature is raised and since this rise of temperature may be considerable (of the order of 150 C. on an average) it will be apparent that the elec trodes supported from the collars are firmly secured to the respective stems. It has been found in practice that when clamp rings of invar are employed about collars of Monel metal, there is no necessity of providing metal gauze or other form of frictional surface between the collar and the stem, thus the metal within the tube is reduced to a minimum and the electrode construction simplified.

While I have described my invention more particularly with respect to the use of Monel metal for the collar metal and clamp rings composed of invar, it will be understood that other metals may be employed for the respective metals provided that the clamp ring material has a less COGlfiClBIll) of expansion than that of the collar material.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electrical discharge device, an envelope terminating in a reentrantstem of glass, an electrode within the envelope, means for supporting the electrode from the stem, said means comprising a metallic support member and a metal clamp for securing the support member to the stem, the metal of the clamp having a smaller coeflicient of expansion at the operating temperatures than that of the electrode supporting means and the stem.

2. In an electrical discharge device, an evacuated envelope terminating in a men trant stem of glass, an electrode within the envelope and supported from the stem by means of a collar which embraces the stem, means for rigidly securing the collar to the stem, said means comprising a clamp ring constituted of metal having a smaller coeificient of expansion at the operating temperature than that of the collar, and\the stem.

3. In an electrical discharge device, an evacuated envelope terminating in a reen trant stem of glass, an electrode within the envelope and supported from the stem by means of a collar of Monel metal, and means for rigidly securing the collar to the stem, said means comprising a clamp ring of invarmetal.

In witness whereof, I have hereunto set my hand this 28th day of May, 1929.

WILLIAM N. MISCHLER. 

